Currently, magnetic elements are of interest for a variety of applications. In general, such conventional magnetic elements are magnetic tunneling junctions. FIG. 1 depicts such a conventional magnetic element 10. The conventional magnetic element 10 includes a conventional antiferromagnetic (AFM) layer 12, a conventional pinned layer 14, a conventional tunneling barrier layer 16, and a conventional free layer 18. Other layers (not shown), seed, and/or capping layers may also be used. The conventional pinned layer 14 and the conventional free layer 18 are ferromagnetic. Thus, the conventional free layer 18 is depicted as having a changeable magnetization 19. The nonmagnetic tunneling barrier layer 16 is typically an insulator. The magnetization 15 of the pinned layer 14 is pinned in a particular direction by the AFM layer 12. The magnetization 19 of the free layer 18 is free to rotate, typically in response to an external magnetic field.
Depending upon the orientations of the magnetization 19 and 15 of the conventional free layer 18 and the conventional pinned layer 14, respectively, the resistance of the conventional magnetic element 10, respectively, changes. When the magnetization 19 of the conventional free layer 18 is parallel to the magnetization 15 of the conventional pinned layer 14, the resistance of the conventional magnetic element 10 is low. When the magnetization 19 of the conventional free layer 18 is antiparallel to the magnetization 15 of the conventional pinned layer 14, the resistance of the conventional magnetic element 10 is high. To sense the resistance of the conventional magnetic element 10, current is driven through the conventional magnetic element 10. Current could be driven in a CPP (current perpendicular to the plane) configuration, perpendicular to the layers of conventional magnetic element 10 up or down, in the z-direction as seen in FIG. 1. Based upon the output, it can be determined whether the resistance of the conventional magnetic element 10 is high or low. When the magnetic element is used for logic application, typically a high resistance state (free layer magnetization 19 antiparallel to the pinned layer magnetization 15) corresponds to a logical zero, “0”. A low resistance state (free layer magnetization 19 parallel to the pinned layer magnetization 15) corresponds to a logical one, “1”.
One application that is of interest is the use of the conventional magnetic element 10 in reconfigurable structures that perform multiple logic operations such as AND, OR, NAND, and NOR functions. Logic functions are traditionally performed using conventional transistor based logic. Conventional transistor based logic circuits are designed to perform one logic operation per design. Thus, the transistor based logic cells cannot be reconfigured to perform alternate operations. It would, therefore, be desirable to perform such logic operations using reconfigurable technology, such as magnetic technology.
Although conventional magnetic elements, such as the conventional magnetic element 10, can be used in reconfigurable logic design, one of ordinary skill in the art will readily recognize that current designs have serious drawbacks. For example, most conventional reconfigurable logic designs using the conventional magnetic element 10 require multiple conventional magnetic elements 10 per cell. See, for example, R. Richter, H. Boeve, L. Bar, J. Bangert, U. K. Klostermann, J. Wecker and G. Reiss, “Field programmable spin-logic based on magnetic tunneling elements” in Journal of Magnetism and Magnetic Materials, vol. 240 (2002) pp 127–129 or W. Black and B. Das, “Programmable logic using giant-magnetoresistance and spin-dependant tunneling devices” in Journal of Applied Physics, vol. 87 (2000) pp 6674–6679. Alternatively, other conventional reconfigurable logic designs that utilize conventional magnetic elements 10 involve complex interconnection architectures. See, for example, S. Nakamura and S. Haneda, “Magnetic logic element and magnetic logic element array”, U.S. Patent Publ. # 2003/0227807 or A. Ney, C. Pampuch, R. Koch and K. H. Ploog, “Programmable computing with a single magnetoresistive element” in Letter to Nature, vol. 425 (2003) pp 485–487. Multiple conventional magnetic elements 10 per cell and complex interconnection architectures are a barrier to using magnetic elements in higher density, relatively easily fabricated reconfigurable logic circuits.
Accordingly, what is needed is a method and system for providing reconfigurable logic that utilizes magnetic elements while maintaining a simpler structure. The present invention addresses such a need.